There may exist a multi-RAT user equipment capable of accessing two or more radio access technologies (RATs). In order to access a specific RAT, a connection to the specific RAT is established based on a request of a user equipment and then data transmission and reception can be performed. Yet, although the multi-RAT UE is capable of accessing two or more RATs, the multi-RAT UE is unable to access multiple RATs at the same time. In particular, although a user equipment is equipped with a multi-RAT capability, the user equipment is unable to simultaneously transmit and receive data via RATs different from each other.
Since a legacy multi-RAT technology corresponds to a switching-based multi-RAT technology, a data is transmitted in a manner of being switched by a different RAT. Hence, it is difficult to select a RAT appropriate for a flow characteristic. A solution for the aforementioned problem is not proposed yet.